The mechanism of hypogonadism was studied in a 63-year-old man with idiopathic hemachromatosis. Basal levels of thyroid, prolactin, cortisol, and growth hormones were normal and responded normally to appropriate provocative stimuli. Basal testosterone and gonadotropin levels were low. There was inadequate gonadotropin response to luteinizing hormone-releasing hormone and clomiphene citrate stimulation. Testosterone response to human chorionic gonadotropin was normal. Hypothalamic-pituitary dysfunction resulting in impaired gonadotropin secretion appears to be the cause of hypogonadism in hemochromatosis.